Differential equation

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#1
iam not able to solve Q 12.
I solved the diff eq and got 1/100[ln(P/100-P)=Kt/100+C
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2 weeks ago
#2
(Original post by Shas72)
iam not able to solve Q 12.
I solved the diff eq and got 1/100[ln(P/100-P)=Kt/100+C
You use the two initial conditions to determine k and c.
Note I guess P is in millions of people?
Last edited by mqb2766; 2 weeks ago
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#3
(Original post by mqb2766)
You use the two initial conditions to determine k and c.
Note I guess P is in millions of people?
So when P= 50 million , t=0 and P= 60million, t=10 years right?
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2 weeks ago
#4
(Original post by Shas72)
So when P= 50 million , t=0 and P= 60million, t=10 years right?
P=50 when t=0. Otherwise it doesn't make sense. It should state in the question though.
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#5
(Original post by mqb2766)
P=50 when t=0. Otherwise it doesn't make sense. It should state in the question though.
Ok i have also done a silly mistake. Let me work it out and see if I get the right ans. Thanks!!
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#6
(Original post by mqb2766)
P=50 when t=0. Otherwise it doesn't make sense. It should state in the question though.
So c=0 and k=1/10ln3/2 right?
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2 weeks ago
#7
(Original post by Shas72)
So c=0 and k=1/10ln3/2 right?
I've not worked it through fully, but upload your working if you want it checked.
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#8
p

(Original post by mqb2766)
I've not worked it through fully, but upload your working if you want it checked.
ok sure.
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#9
(Original post by mqb2766)
I've not worked it through fully, but upload your working if you want it checked.
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2 weeks ago
#10
Looks fine so far
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#11
(Original post by mqb2766)
Looks fine so far
So when P=60, t=10 right?
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2 weeks ago
#12
(Original post by Shas72)
So when P=60, t=10 right?
As far as I can tell. That will give you k.
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#13
(Original post by mqb2766)
As far as I can tell. That will give you k.
Yeah I know that. So I got k =1/10ln1.5
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2 weeks ago
#14
(Original post by Shas72)
Yeah I know that. So I got k =1/10ln1.5
Seems ok.
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#15
(Original post by mqb2766)
Seems ok.
I dont get the ans. The textbook ans is 73.4 million correct to 3sf
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2 weeks ago
#16
(Original post by Shas72)
I dont get the ans. The textbook ans is 73.4 million correct to 3sf
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2 weeks ago
#17
(Original post by Shas72)
iam not able to solve Q 12.
I solved the diff eq and got 1/100[ln(P/100-P)=Kt/100+C
Why make things difficult for yourself? Try rotating your book 180 degrees. That should make things easier.
1
2 weeks ago
#18
(Original post by Plücker)
Why make things difficult for yourself? Try rotating your book 180 degrees. That should make things easier.
I'm sure OP is reading their book the right way up. They have just uploaded the image wrong...
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2 weeks ago
#19
(Original post by 5hyl33n)
I'm sure OP is reading their book the right way up. They have just uploaded the image wrong...

You might be right.
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#20
(Original post by mqb2766)
Ok let me try
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